1. Field of the Invention
The present invention relates to an exposure amount control device for a camera for measuring the light reflected from the film plane, particularly for obtaining a proper exposure taking the difference of the reflexibility of the films to be used into consideration.
2. Description of the Prior Art
In case of the conventional camera for controlling the exposure amount by measuring the light reflected from the film plane the reflexibility of the film plane is supposed to be constant regardless of the kinds of the films while the reflexibility of the film plane is made equal to that of the shutter plane, whereby the light reflected from the film plane and that from the shutter plane are measured so as to control the exposure amount.
However, in reality of the reflexibility of the films normally used varies within .+-.0.2 step in the number of steps, so that when films with different reflexibility are loaded in a camera of the conventional film plane light measuring system, the exposure control system operates without compensating the difference of the reflexibility of films so that a proper exposure can not be obtained. Namely, even if a picture is taken with the same film sensitivity and under the same photographing conditions, the higher the reflexibility of the film plane is, the more light is sensed with the light sensing element so that the shutter closes earlier than the proper time and the exposure amount is smaller, while the lower the reflexibility of the film plane is, the less light sensed with the light sensing element so that the shutter time becomes longer than the proper one and the exposure amount is larger.
Further, in case of a camera with the conventional film plane light measuring system, the shorter the shutter time is, the larger the ratio for measuring the light reflected from the shutter plane to that reflected from the film plane is, so that although the reflexibility of the film plane is supposed to be equal to that of the shutter plane it is impossible to consider the reflexibility of the film plane equal to that of the shutter plane because the reflexibility of film is different in accordance with the kind of film, whereby it is difficult to obtain a proper exposure.
A purpose of the present invention is to eliminate the afore mentioned shortcoming by means of compensating the exposure amount with the output of the compensation light measuring circuit by providing a film plane reflexibility light measuring circuit beside the exposure control light measuring circuit for measuring the light reflected from the shutter plane and that from the film plane.
Another purpose of the invention is to compensate the exposure amount by means of a memory circuit provided in order to store the output of the film plane reflexibility compensation light measuring circuit.
Further another purpose of the present invention is to compensated the exposure amount by means of a comparison circuit provided for comparing the output of the exposure control light measuring circuit with that of the film plane reflexibility compensation light measuring circuit.